Paint applying and drying system

ABSTRACT

A system for continuously applying paint to a continuously moving metal strap and thereafter continuously drying the paint on the metal strap. The system disclosed herein includes a paint pot wherein the paint is electrophoretically applied as a uniform coating to the metal strap passing through the paint pot, nd a drying station disposed above the paint pot includes a number of induction coils through which the painted metal straps pass and have induced therein eddy currents which heat the metal strap to dry the paint thereon. Means are provided automatically to maintain the level of the paint and the concentration of solids in the paint contained in the paint pot, and means are provided automatically to vary the output from the induction coils in response to the speed and temperature of the metal strap to maintain constant the temperature of the metal strap exiting from the drying station.

United States Patent Richard S. Patton Flossmoor;

Naaman II. Keyser, I-Iinsdale; Vernon L. Langdon, Tinley Park; Victor D.Beaucaire, I-Iomewood; Louis A. Marlin, Crestwood,

[72] Inventors all of Ill. [21] Appl. No. 888,215 [22] Filed 29, 1969[45] Patented [73] Assignee Oct. 26, 1971 Interlake Steel CorporationChicago, Ill.

[54] PAINT APPLYING AND DRYING SYSTEM [5 6] References Cited UNITEDSTATES PATENTS Primary Examiner-John H. Mack Assistant Examiner-A. C.Prescott Attorney-Prangley, Clayton, Mullin, Dithmar & Vogel ABSTRACT: Asystem for continuously applying paint to a continuously moving metalstrap and thereafter continuously drying the paint on the metal strap.The system disclosed herein includes a paint pot wherein the paint iselectrophoretically applied as a uniform coating to the metal strappassing through the paint pot, nd a drying station disposed above thepaint pot includes a number of induction coils through which the paintedmetal straps pass and have induced therein eddy currents which heat themetal strap to dry the paint thereon. Means are provided automaticallyto maintain the level of the paint and the concentration of solids inthe paint contained in the paint pot, and means are providedautomatically to vary the output from the induction coils in response tothe speed and temperature of the metal strap to maintain constant thetemperature of the metal strap exiting from the drying station.

PATENTEDnm 26 um SHEET 1 OF 6 FI6.I

INVENTORS Y RICHARD S. PATTON NAAMAN H. KEYSER VERNON L. LANGDON VICTORD. BEAUCA/RE A. MARLIN Lou s PATENTEDum 26 I9?! 3. 6 1 6 459 SHEET u BF6 PAINT APPLYING AND DRYING SYSTEM This invention relates to a systemfor continuously applying paint to a continuously moving metal strap andcontinuously drying the paint thereon, and more particularly, thisinvention relates to a system in which the paint is electrophoreticallyapplied to a metal strap and induction heating is used to dry the paintby heating the metal strap which carries the paint thereon.

It is an important object of the present invention to provide a systemfor continuously applying paint to a continuously.

moving metal strap and continuously drying the paint thereon, the systemcomprising a paint-applying station including a paint pot and anelectrophoretic paint-distributing apparatus therein for applying auniform coating of paint of the metal strap, a paint-drying stationincluding an induction coil for heating the metal strap to dry the paintthereon, drive mechanism for continuously passing the metal strap from asource thereof through the paint pot and the electrophoreticpaint-distributing apparatus and then through the induction heatingcoil, a source of paint solids in communication with the paint pot, mansfor continually sensing the power consumed in the electrophoreticpaint-distributing apparatus, means for continually sensing theconcentration of paint solids in the paint pot, a first control circuitresponsive to the power consumption sensing means and the paint solidsconcentration sensing means for maintaining the concentration of paintsolids and the paint level in the paint pot within predetermined values,a variable power supply for the induction heating coil for controllingthe output therefrom, means for sensing the speed of movement of themetal strap with respect to the induction coil, means for sensing thetemperature of the painted metal strap immediately after passage thereoffrom the induction heating coil, and a second control circuit responsiveto the metal strap speed sensing means and to the painted straptemperature sensing means for controlling the variable power supply andthus the heating produced by the induction heating coil to heat thepainted metal strap to a predetermined temperature at thetermperature-sensing means, whereby to apply to the metal strap auniform coating of paint uniformly dried thereon throughout the lengththereof.

Another object of the present invention is to provide a system of thetype set forth, in which a source of paint diluent is provided incommunication with the paint pot and means are provided for continuallysensing the level of paint in the paint pot, and maintaining the levelof the paint in the paint pot within a predetermined value.

Another object of the presentinvention is to provide a system of thetype set forth, in which a paint solids pump is provided incommunication with the paint solids source for withdrawing apredetermined amount of paint solids from the paint solids source, and ablender is provided in communication with the paint solids pump formixing the paint solids withdrawn by the paint solids pump from thepaint solids source with the paint in the paint pot to maintain constantthe concentration of paint solids within a predetermined value.

Still another object of the present invention is to provide a system ofthe type set forth, in which there are provided a source of paintdiluent in connection with the paint pot, a paint solids pump incommunication with the paint solids source for withdrawing apredetermined amount of paint solids from the paint solids source, ablender in communication with the paint solids pump for mixing the paintsolids withdrawn by the paint solids pump from the paint solids sourcewith the paint in the paint pot, means for continually sensing the levelof paint in thepaint pot, and a second control circuit responsive to thepaint level sensing means for connecting the source of paint diluent tothe paint pot for maintaining the level of paint within a predeterminedvalue.

Still another object of the present invention is to provide a system forcontinuously applying a paint to a continuously moving metalstrap, saidsystem comprising a paint-applying station including a paint pot and anelectrophoretic distributing apparatus therein for applying a uniformcoating of paint to the metal strap, drive mechanism for continuouslypassing the metal strap from a source thereof through the paint pot andthe electrophoretic distributing apparatus, a source of paint solids incommunication with the paint pot and a source of paint diluent incommunication with the paint pot, means for continuously sensing thepower consumed in the electrophoretic paint-distributing apparatus,means for continually sensing the concentration of the paint solidsinthe paint pot, means for continuously sensing the level of paint inthe paint pot, and a control circuit responsive to the power consumptionsensing means and the paint solids concentration sensing means and thepaint level sensing means for maintaining the concentration of paintsolids and the paint level in the paint pot within predetermined values,whereby to apply to the metal strap throughout the length of the strappassing through the paint pot a uniform coating of paint containing asubstantially uniform amount of paint solids therein.

A further object of the present invention is to provide a system forcontinuously applying paint as herein set forth, in which there isprovided a paint solids pump in communication with the paint solidssource for withdrawing a predetermined amount of paint'solids from thepaint solids source and a blender in communication with the paint solidspump for mixing the paint solids withdrawn by the paint solids pump fromthe paint solids source with the paint in the paint pot to maintain theamount of paint solids in the paint pot within a predetermined value.

A further object of the present invention is to provide a system forcontinuously applying paint to a continuously moving strap of the typeset forth, in which there are provided a source of paint diluent inconnection with the'paint pot, means for continuously sensing the levelof paint in the paint pot, and a second control circuit responsive tothe paint level sensing means for connecting the source of paint diluentto the paint pot for maintaining the level of paint within apredetermined value.

A further object of the present invention is to provide a system forcontinuously drying a painted continuously moving metal strap, saidsystem comprising a drying station including an induction coil forheating the metal strap to dry the paint thereon, drive mechanism forcontinuously passing the metal strap through the induction heating coil,a variable power supply for the induction heating coil for controllingthe output therefrom, means for sensing the speed of movement of themetal strap with respect to the induction heating coil, means forsensing the temperature of the painted metal strap immediately after thepassage thereof from the induction heating coil, and a control circuitresponsive to the metal strap speed sensing means and to the paintedmetal strap temperature sensing means for controlling the variable powersupply and thus the heating produced by the induction heating coil toheat the painted metal strap to a predetermined temperature at thetemperature sensing means, whereby to dry the paint on the metal strapthroughout the length thereof passing through the induction heatingcoil.

A still further object of the present invention is to provide a systemfor continuously drying a painted continuously moving metal strap inwhich the control circuit includes limit means responsive to the metalstrap sensing means for deenergizing the induction heating coil when thespeed of the metal strap with respect to the induction heating coil isbelow a predetermined value.

The invention, both as to its organization and method of operation,together with further objects and advantages thereof, will best beunderstood by reference to the following specification taken inconnection with the accompanying drawings in which:

FIG. I is a schematic and diagrammatic illustration of the system of thepresent invention for continuously applying paint to a continuouslymoving metal strap and continuously drying the paint thereon;

FIG. 2 is a schematic and diagrammatic view of the continuous paintapplying system of the present invention;

FIG. 3 is a side elevational view partly in section of theelectrophoretic paint-distributing apparatus shown in FIG. 2 taken alongline 33 thereof;

FIG. 4 is a front plan view of the electrophoretic paint-distributingapparatus shown in FIG. 3;

FIG. 5 is a side elevational view of the continuous drying station ofthe present invention;

FIG. 6 is a view partially in section of the drying station shown inFIG. 5 taken along line 66 thereof;

FIG. 7 is a block diagram of the control system for the continuous paintapplying system of the present invention; and

FIG. 8 is a block diagram of the control system for the paint dryingstation of the present invention.

There is disclosed hereinafter a system 100 for continuously applyingpaint to a continuously moving metal strap 50 and continuously dryingthe paint thereon, the metal strap 50 being driven along a predeterminedpath by a drive mechanism 75 through a paint-applying station 105 andthen through a paint-drying station 110. As seen particularly in FIG. 1,the metal strap 50 passes along the predetermined path into a paint pot115 in which paint is electrophoretically applied to the metal strap 50,and thereafter a painted metal strap 51 passes upwardly through aplurality of heating units 245 where the paint uniformly applied in thepaint pot 115 is dried by the induction heating of the painted metalstrap 51 to produce a metal strap 52 having a uniform coating of paintapplied thereto and dried thereon.

FIG. 2 shows the spatial relationship between some of the apparatusconnected with the electrophoretic deposition of paint on the metalstrap 50, the paint-applying station 105 including a paint pot 115, avariable power supply source 170, a paint solids source 180, a paintrefrigeration unit 190 and a paint diluent source 177. There is furthershown a drive mechanism or bridle 75 for continuously moving the metalstrap 50 along its predetermined path, a paint-holding tank 188 forstorage of paint during maintenance periods in which the paint pot 115is serviced and a pair of recirculating pumps 185 and 186, for a purposehereinafter explained.

With particular reference to FIGS. 2, 3 and 4, there is shown thepaint-applying station 105 including the paint pot 115, the paint pot115 including an enclosed metal container 116 supported by twospaced-apart generally parallel I-beams 117 each of which rests on agrouting 118, the paint pot 115 being provided with a synthetic plasticresin liner 119 on the inside thereof and firmly connected to the metalcontainer 116. A rotatable shaft 120 is disposed within the paint pot115 near the bottom thereof and is positioned generally horizontally,the shaft 120 being joumaled at either end thereof in a bearing 12], thebearings 121 are connected to and supported by a flange 122, the flange122 being fixedly secured to the metal container 116. A plurality offlanged wheels [25 are fixedly connected to the shaft 120 and arerotatable therewith, the flanged wheels 125 each supporting a metalstrap 50 as particularly shown in FIG. 4. The metal strap 50 may be asingle strap having a substantial width or, as in the case herein shown,the metal strap 50 may comprise a plurality of individual strapsarranged side by side in a row, twelve such straps being shown. Theflanged wheels 125 serve to maintain the straps 50 in their spatialrelationship one to the other, thereby to prevent them from becomingdisoriented.

The metal straps 50 enter the paint-applying station 105 by passing overand in contact with an anode roll 130, the anode roll 130 beingjournaled on a shaft 131 positioned above the paint pot 115 and held inplace by a pair of spaced-apart supports 132 fixedly connected toseveral I-beams 133 hung from a mezzanine floor or rafter 134. The anoderoll 130 receives its charge through the shaft 131 which passes througheach of the supports 132 and is electrically insulated therefrom by theinsulators 137, the shaft 131 carrying at both ends thereof a connectorI35, each of the connectors 135 being connected to a slip ring 136. Thesliprings 136 are connected to the variable power supply 170 by means ofa cable 140 which leads from the power supply 170 to a pull box 141,there being two pull boxes 141, each one of which being associated witha respective slip ring 136. A pair of connecting cables I42 serve totransmit the current from the pull boxes 141 to the slip rings 136, thesliprings 136 being of conventional construction and operating in aconventional manner to provide a charge from the variable power supply170 to the anode roll 130. The sliprings 136 serve to transmit apositive charge to the anode roll 130 and thereby a positive charge tothe metal strap 50 contacting and passing over the anode roll 130.

There is further provided a plurality of cathode plates 145, the cathodeplates 145 being positioned within the paint pot and arranged verticallyin two sets each containing three pairs of cathode plates 145, each pairincluding two plates 145 spaced apart and generally parallel one to theother. The cathode plates 145 are fixedly secured at each end thereof tovertically disposed frame ember 146, the frame members 146 beingelectrical conductors each depending from an angle iron 147 resting onan insulator 148 all of which is disposed on a support member 149. Thesupport member 149 extends entirely across the top of the paint pot 115thereby to support the cathode plates 145 in their positions within thepaint pot 115 and electrically to insulate the cathode plates 145therefrom. To this end, the line 119 also insulates the paint pot 115from the electrically charge paint therein. As may be seen, there aretwo sets of cathode plates 145, each set being disposed to one side ofthe flanged wheels so that the metal strap 50 passes between the cathodeplates 145 when entering the paint pot 115 from the anode roll and whenexiting the paint pot 115 to be transported to the paint-drying station110.

The cathode plates 145 are electrically connected to the variable powersupply 170 and the cable leading therefrom by a plurality of pull boxes151, there being three such pull boxes disclosed herein. The cable I40from the variable power supply 170 leads to each of the pull boxes I51and a cable 152 thereafter leads from the pull box 151 to each of theframe members 146 supporting, as shown herein, three verticallyspaced-apart cathode plates 145, each of the cables 152 leading to aconnector 153 disposed on an angle iron I54 suitably connected tocorresponding one of the angle irons 147, such as by welding. It is seentherefore, that the cathode plates are electrically connected to thevariable power supply 170 due to the electrical conducting frame 146which is electrically connected to the cables 152 and thereby the cable140 leading from the variable power supply 170.

There is further disclosed a paint level sensing device positioned abovethe paint pot 115 for sensing the paint level therein, the paint levelbeing denoted by the line in phantom, the paint level sensing device 160including a sensor 161 extending downwardly into the paint pot I15 and acable 162 leading from the sensing device 160 to a junction box 163 andthereafter to a recorder (not shown). There is further provided anaperture 164 in the paint pot 115 for various piping connections, forinstance, a paint return pipe. When the painted metal strap 51 leavesthe paint pot 115 after having paint electrophoretically applied theretoit passes through a sponge 242 positioned above the paint pot 115, thesponge 242 serving to wipe excess paint from the painted metal strap 51,the sponge 242 being suitably connected to an angle iron 243 and asupport 244.

As is known, in the electrophoretic deposition of paint, the substrateto which the paint is to be applied, in this case the metal straps S0,is provided with a positive charge and the paint solid particles areprovided with a negative charge. In the present case the metal straps 50pass over the anode roll 130 to have imparted thereto a positive chargeand the paint particles in the paint pot 115 come in contact with thecathode plates 145 to have imparted thereto a negative charge. When thepaint particles carrying a negative charge come into proximity to themetal straps 50 carrying a positive charge the negatively charge paintparticles are attracted thereto, the advantage of the electrophoreticdeposition of paint being that the paint is attracted to all thesurfaces of the metal straps 50 paint-applying station to provideuniformly coated metal straps 51. As the paint builds up on the metalstraps, the current density in the metal straps 51 drops as the filmthickness increases until current flow stops and there is no oredeposition of paint solids on the painted metal straps 51. The variableswhich must be controlled in order adequatelyto provide for theelectrophoretic deposition of paint on continuously moving metal straps50 are the solids concentration of that paint, the temperature of thepaint, the speed of the metal straps 50 passing through the paint andthe voltages used to produce the current densities applied to the metalstraps 50. The control system for the aforementioned variables willhereinafter be explained.

It can be seen therefore that there is provided herein a 105 including apaint pot 115 into which the unpainted metal straps 50 are passed. Aftercontacting an anode roll 130 which imparts to the straps 50 a positivecharge, the straps 50 pass through a cathode area around a flanged wheeland upwardly through a second cathode area to have electrophoreticallydeposited thereon paint solids from a paint contained within the paintpot 115 and maintained at a level 165 to produce uniformly painted metalstraps 51. The control system for varying the current fed to the anoderoll 130 and the cathodes 145, for maintaining the paint level as at165, for maintaining the paint composition at a predetermined paintsolids concentration and for maintaining the temperature of the paint ata predetermined level will be hereinafter disclosed.

After the painted metal straps 51 exit from the paint-applying station105 with a uniform coating of paint thereon, the paint containing asubstantially uniform amount of paint solids therein, the painted metalstraps 51 pass upwardly to the paint-drying station 110, thepaint-drying station 110 including a plurality of spaced-apart heatingunits 245, there being five such heating units shown herein. Each of theheating units 245 include an induction heating coil 250, each of theinduction heating coils 250 being in the form of a hollow metal straphaving a rectangular cross section. The induction heating coils 250 arepositioned inside the heating unit 245, the heating units 245 includingtwo spaced-apart vertically disposed end walls 251 resting on twospaced-apart horizontally disposed bottom insulating boards 252, thebottom insulating boards 252 forming therebetween a slit for the passageof the painted metal straps 51 therethrough. Bottom angle irons 253serve to connect the end walls 251 with the bottom insulating boards 252and top angle irons 254 serve to connect the end walls 251 with a pairof horizontally disposed spaced-apart top mounting boards 255, the topmounting boards 255 also being spaced apart to form therebetween a slitfor the passage therethrough of the painted metal straps 51. Each of theheating units 245 is held in place above the paint-applying station 105by a support structure including four vertical support frame members 256interconnected by horizontal support frame members 257 and a pair ofcoil support brackets 258 suitably supporting a respective one of thebottom insulating boards 252. The entire support structure is positionedwithin a tower 260 surrounding both the paint-drying station 110 and thepaint-applying station 105, the tower 260 including vertical supportmembers 261 and horizontal support members 262. The tower 260 furtherincludes a plurality of idler rollers 263 which serve to position thestraps 50 upon entering the paint-applying station 105 and then exitingthe paint-applying station as painted straps 51 and pass upwardlythrough the paint-drying station 110 and exiting therefrom as driedpainted straps 52.

The dried metal straps 52 thereafter pass over several of the idlerrollers 263 and out of the tower 260 for further processing down theline, there being provided a plurality of aligning wheels 265 further tomaintain the straps 52 in their sidc-by-side arrangement. As the paintedmetal straps 51 passes upwardly through the slits formed by the bottominsulating boards 252 and the top mounting boards 255 and through theinduction heating coils 250, eddy currents are induced in the metalstraps 51 by the passage thereof through the fields of the inductionheating coils 250, as hereinafter explained, to provide heating withinthe straps 51, thereby to dry the paint thereon from the inside of thepaint coating to the outside to provide a uniform paint coating withoutthe usual blisters caused by trapped air and the like formed when paintdries from the outside in. The power supplied to the induction heatingcoils 250 together with the amount of metal passing through the fieldsand the speed of the straps determine the amount of heating induced inthe painted metal straps 51, the power supplied to the induction heatingcoils 250 being controlled both by the speed of the meta] straps 51 asmeasured by a tachometer 320 and by the temperature of the dried metalstraps 52 as it exits from the paint-drying station as measured by aninfrared sensor 340, all as hereinafter explained.

With particular reference to FIG. 7, the control system for thepaint-applying station 105 will hereinafter be described,

the control system including a rectifier for a variable power sourceconnected as by a conductor 210 to a control 171 therefor, the control171 serving to provide means for manually varying the output from thevariable power source 170. The output from the power source 170 istransmitted as by a conductor 211 to a current recorder 172 and thenceby conductor 213 to the anode 130 and by conductor 212 to contactors173. The contactors 173 are connected to a plurality of ammeters 174,there being one ammeter 174 for each cathode plate 145. An emergencystop 175 is provided and is connected as by a conductor 221 to thecontactors 173 thereby to provide manual means for halting the flow ofcurrent to the cathodes 145.

There is further provided a paint diluent source 176, as shown here thecity water supply, connected by a pipe 238 to deionizing tanks 177, thedeionizing tanks 177 serving to deionize and demineralize the citywater. The deionized water from the deionizing tanks 177 flows through apipe 239, into the paint pot 115, via a solenoid valve 178, controlledby a flow control 179, the flow control 179 being suitably connected bya conductor 222 to the float switch 160 disposed within the paint pot115. A paint solids source in the form of the paint solids drums 180 isprovided, and since the paint solids are extremely viscous as providedthere is also a drum warmer 181 for warming the paint solids withinthese paint solids drums 180. A pipe 231 connects the paint solids drums180 with a paint solids pump 182, that paint solids pump 182 serving towithdraw paint solids from the drums 180.' The ,paint solids pump 180may be an air-driven motor mounted on the drums and pumps the paintsolids from the drums 180 through the piping 231 to an in-line blender183. Paint in the paint pot 115 is withdrawn therci'rom through a pipe230 by the action of a recirculating pump 185, there also being provideda spare recirculating pump 186 suitably isolated from the line by avalve 187. The paint coming from the paint pot 115 in the line 230 ismixed with solids withdrawn by the paint solids pump 182 and fed as at232 to the in-line blender 183. The mixed paint solids and paint exitsfrom the in-line blender as at 233 and flows through the recirculatingpump'185 (unless the valve 187 is open in which case the mixed paint andpaint solids flows through line 234 and the spare recirculating pump186) via the line 235 to the paint refrigerator 190 wherein the paint iscooled and returned to the paint pot throughout the pipe 236. The paintrefrigerator 190 is run by a motor 191 and is connected to theplant-cooling system 192 by means of piping 237. There is furtherprovided a paintholding tank 188 connected to the pipes 233 and 235, thepaint-holding tank 188 serving to hold the paint when the paint pot 115is being serviced. As the recirculating pump 185 or the spare pump 186is continuously running, paint is constantly being withdrawn from thepaint pot 115 and circulating through the aforementioned piping.

A connection to the line 235 is provided to bleed a small part of thepaint from the line 233 to a viscometer 195, the viscometer 195 beingof;:thc pneumatic type and serving to measure the viscosity of the paintin the paint pot. Paint is returned to the paint pot from the viscometer195 by the pipe 240 thereby to provide a closed loop through theviscometer 195. A signal from the viscometer 195 is fed as by anelectrical conductor 215 to a viscosity recorder 196 and a temperaturerecorder 197, the output from the temperature recorder 197 being fed byconductor 217 to a refrigerator control 198, which control 198 isconnected as by conductor 218 to the paint refrigerator 190, thereby tocontrol the temperature of the paint in the paint pot 115. The outputfrom the viscosity recorder 196 is carried as by the conductor 215 to apaint feed control 201, the paint feed control 201 also receiving aninput from an ampere-hour recorder 200, the ampere-hour recorder 200receiving an input from the current recorder 172 connected to theampere-hour recorder 200 by a conductor 212. The output from theampere-hour recorder 200 is carried as by a conductor 214 to the paintfeed control 201, the paint feed control 201 receiving inputs from boththe ampere-hour recorder 200 and the viscosity recorder 196 andgenerating a signal which is carried by a conductor 216 to the paintsolids pump 182. There is further provided a tachometer 205 to measurethe speed of the metal strap 50 entering the paint pot 115, thetachometer 205 having an output therefrom fed to the rectifier for thevariable power source 170 as by conductor 219 and having an outputtherefrom also fed as by a conductor 219 to a line relay 206 and fromthere by a conductor 220 to the contactors 173.

In operation, the amount of paint deposited on the metal strap 50 iscontrolled in part by the amount of current fed to the cathodes 145 andthe anodes 130 which is fundamentally controlled by tachometer 205.Since the faster the metal strap 50 passes through the painting station105 the less time it will reside in the paint pot 115 the greater willhave to be the current fed to the anode 130 and the cathodes 145 todeposit the same amount of paint on the straps 50 as would be depositedon'the metal straps 50 if passed through the paint pot 115 at a slowerspeed with a lower current being supplied to the anode 130 and thecathodes 145. It is seen therefore that the principal control for theamount of power supplied from the variable power source 170 is providedby the tachometer 205 which measures the line speed of the metal straps50. The amount of current fed to the anode 130 and the cathodes 145determines, for the most part, the amount of paint deposited on he metalstraps 50, current densities in the strap 50 being from about 0.1 toabout +amp./ft., the power supply 170 producing from about 50 to about250 volts. 1n the electrophoretic deposition of paint the solids contentof the deposit coating is generally between 80 and 95 percent with onlyfrom about 5 to percent of the coating being the paint diluent;therefore, it is seen that as the paint coating is deposited on themetal strap the paint will become deficient as paint solids, therebynecessitating the addition of paint solids to the paint to maintain theconcentration of solids in the paint between about 5 and about 15percent. To this end the ampere-hour recorder 200 records the amount ofcurrent fed to the anode 130 and the cathode 145, which amount ofcurrent is proportional to the amount of paint being deposited on themetal strap 50 as it passes through the paint. The ampere-hour recorder200 sends a signal to the paint feed control 201 which counts thesignals form the ampere-hour recorder 200 and at a predetermined timesends a signal to the paint solids pump 182 which activates the same towithdraw a predetermined amount of paint solids from the drum 180. Thepaint solids pump 182 operates for a predetermined time to withdraw thepredetermined amount of paint solids from the drum 180 and feeds thepaint solids to the in-line blender 183 which mixes the withdrawn paintsolids with the paint withdrawn from the tank by the recirculating pump185. The mixed paint solids and the paint are thereafter pumped to thepaint refrigerator 190. Since the electrophoretic deposition of paintcreates heat, it is necessary to remove heat from the paint in order tomaintain it at the desired temperature, which temperature is betweenabout 75 to about 100 F., the paint refrigerator 190 being controlled bythe refrigerator control 198 which in turn receives its signal from atemperature recorder 197 associated with the viscosity recorder 196. Thetemperature of the paint is important not only because of theelectrophoretic deposition process but also because the viscositymeasurement of the paint will vary according to the temperature thereof,thereby it being important that the paint be within a certaintemperature range to provide the proper viscosity measurement.

The level of paint in the paint pot 115 is maintained at a predeterminedlevel by the addition of the paint diluent, in this case water becausewater-soluble paint solids are used herein, as controlled by the floatswitch 160. The sensor 161 sends a signal when the paint level 165 fallsbelow a predetermined point at which time the float control 179 isoperated bya solenoid 178 to admit deionized water or paint diluent intothe paint pot 115. When the paint level reaches a certain point, thefloat switch 160 sends a signal which causes the solenoid valve 178 toclose thereby stopping the addition of paint diluent to the paint pot115.

The viscosity of the paint in the paint pot 115 is fundamentallymaintained by the addition of diluent in response to the level of thepaint in the paint pot 115 and the periodic addition of paint solids bymeans of activation of the paint solids pump 182 in response to acertain amount of current as recorded by the ampere-hour recorder 200.When the paint viscosity remains within a predetermined range, the paintfeed control 201 sends a signal to the paint solids pump 182 in responseto the amount of current fed to the cathodes 145 as recorded by theampere-hour recorder 200; however, if a malfunction oc curs or anunusual circumstance occurs and the viscosity of the paint varies beyonda predetermined amount, a signal from the viscosity recorder 196 to thepaint controller 201 will cause the addition of a larger amount of paintsolids to the paint, when the viscosity of the paint is too low, or willresult in fewer additions of paint solids to the paint when theviscosity of the paint is too high. Since the paint solids pump 182 isessentially a batch operation in which the paint solids pump 182operates for a given amount of time in response to a signal from thepaint feed controller 201, variation in the paint viscosity is easilyattained either by adding as additional batch operation of the paintsolids pump 182 in response to a signal from the viscosity recorder 196through the paint feed control 201 or by the skipping of a cycle of thepaint solids pump 182 thereby to add fewer paint solids to the paint.

it is seen therefore, that there has been provided a system forcontinuously applying paint to a continuously moving metal strap 50. Thesystem comprises a paint-applying station including a paint pot and anelectrophoretic distributing apparatus including cathode plates forapplying a uniform coating of paint to the metal strap 50, drivemechanism 75 for continuously passing the metal strap 50 from a sourcethereof through the paint pot 115 and the electrophoretic distributingapparatus. The system further includes a source of paint solids, such asdrums 180 in communication with the paint pot 115 and a source of paintdiluent such as tanks 177 in connection with the paint pot 115, a paintsolids pump 182 in communication with the paint solids source 180 forwithdrawing a predeten'nined amount of paint solids from the paintsolids source 180, a blender 183 in communication with the paint solidspump 182 for mixing the paint solids withdrawn by the paint solids pump182 from the paint solids source 180 with the paint in the paint pot115. The control system includes the ampere-hour recorder 200 forcontinually sensing the power consumed in the electrophoreticpaint-distributing apparatus, the viscometer for continually sensing theconcentration of the paint solids in the paint pot 115, and a firstcontrol circuit responsive to the ampere-hour recorder 200 and to theviscometer 195 for activating the paint solids pump 182 to withdraw apredetermined amount of paint solids from the paint solids source 180for maintaining the concentration of paint solids within a predeterminedvalue. A level-sensing device 160 is provided for continually sensingthe level of paint in the paintpot 115.

and a second control circuit responsive to the level-sensing device 160for connecting the source of paint diluent 177 to the paint pot 115 formaintaining the level of paint within a predetermined value is alsoprovided to apply to the metal strap 50 throughout the length of thestrap 50 passing through the paint pot 115 a uniform coating of paintcontaining a substantially uniform amount of paint solids therein.

The wet painted straps 51 upon exiting from the paint-applying station105 are transported to the paint-drying station 110. Referring now toFIG. 8, there is disclosed therein a control circuit 275 for the heatingstation 110, the control circuit 275 including a variable power supplyin the form of a function generator 280 connected by an electricalconductor 281 to a three-position switch 282. The three-position switch282 is here shown in the automatic position in which the functiongenerator 280 is connected to a DC amplifier 285 by an electricalconductor from the common terminal of the switch 282; however, the DCamplifier 285 may also be controlled by a signal from a manual control286 in the form of a potentiometer, the potentiometer 286 having oneterminal 287 thereof connected to a ground and the other terminal 289thereof connected to a control voltage 290, the control voltage 290herein being illustrated as lO-volt DC source. The sliding contact onthe potentiometer 286 is connected as by connector 291 to the switch282, whereby the DC amplifier 285 may receive an input signal for themanual control of the circuit 275.

The output from the DC amplifier 285 is fed through a conductor 295,normally closed switch contacts 297 and conductors 299 to each of fiveSCR voltage controls 296, there being one SCR voltage control for eachand every induction heating coil 250. The normally closed switch contact297 provide automatic operation of the control circuit as hereinafterexplained. There is also provided for each and every SCR voltage control296 a pair of normally open switch contacts 298, one of the switchcontacts 298 being connected to the conductor 295 and the other of theswitch contacts 298 being connected to the sliding arm on apotentiometer 300, the potentiometer 300 having one terminal 30l thereofconnected to ground, and the other terminal 302 thereof connected to acontrol voltage from a lO-volt DC source. A relay 305 has one terminal306 thereof connected to ground and the other terminal 307 thereofconnected to a normally open switch 308, the switch 308 being connectedto a l20-volt AC source and being normally open so as to maintain therelay 305 in a position such that the switch contacts 297 are normallyclosed and the switch contacts 298 are normally open, all as hereinafterexplained. The relay 305 has a mechanical connection 310 to each pair ofthe normallyclosed switch contacts 297 and a mechanical connection 311to each pair of the normally open switch contacts 298, whereby closingof the normally open switch 308 energizes the relay 305 to open thenormally closed switch contacts 297 and to close the normally openswitch contacts 298, thereby to provide each of the SCR voltage controls296 with a manually selected voltage from the potentiometers 300 insteadof the automatically selected voltage from the function generator 280through the DC amplifier 285, all as hereinafter explained.

The output from each of the SCR voltage controls 296 is fed viaconductor 315 to an associated RF oscillator 316 and the output from theRF oscillator 316 is connected via a conductor 317, which may be acoaxial cable, to the respective induction heating coil 250, theinduction heating coil 250 being connected as at 318 to ground. As thewet painted metal straps 51 exit from the paint-applying station 105 andpass upwardly through the respective ones of the induction heating coils250, the straps 51 are dried and exit from the topmost of the inductionheating coils 250 as dried metal straps 52, the speed of the dried metalstraps 52 relative to the induction heating coil 250 being measured by atachometer 320. The tachometer 320 sends a signal along a conductor 321indicating the speed of the dried metal straps 52 to a recorder 323 andto a low-speed limit circuit 324 and to one terminal 329 of apotentiometer 330. The potentiometer 330 has the other terminal 331thereof connected to ground and the output from the potentiometer is fedfrom the sliding contact thereof by a conductor 335 to the functiongenerator 280. Temperaturesensing means is provided near the topmost ofthe induction heating coils 250 for sensing the temperature of the driedpainted metal straps 52 upon leaving the drying station 110, thetemperature-sensing means being an infrared sensing head 340 for sensingthe infrared radiation given off by the dried metal straps 52 as at 341and sending a signal along a conductor 342 to a DC amplifier 344. Theoutput from the DC amplifier 344 is conducted via a conductor 345 to therecorder 323 and to a comparator 347, the comparator 347 also receivingan input signal from a potentiometer 350. The potentiometer 350 is thetemperature set potentiometer which feeds to the comparator 347 a signalindicative of the desired temperature of the dried metal straps 52 uponexiting from the topmost induction heating coil 250. The temperature setpotentiometer 350 has one terminal 351 thereof connected to ground andthe other terminal 352 thereof connected to a l0-volt DC source. Theoutput from the sliding contact of the temperature set potentiometer 350is fed by a conductor 355 to the comparator 347 and the output from thecomparator 347 is fed via a conductor 358 to a DC amplifier 360. The DCamplifier 360 also receives an input from the low-speed limit circuit324 via a conductor 325. The DC amplifier 360 has its output signal fedvia a conduction 361 to a multiposition switch 362, the switch 362connected in its third position, as is herein shown, to a reversiblemotor 365, the reversible motor 365 having its output fed, as shown bydotted line 370, mechanically to position the slide on the potentiometer330, thereby to combine in the output signal from the potentiometer 330the signal from the tachometer 320 and the signal from the temperaturesensor 340.

As the metal straps 51 exit from the paint-applying station and passupwardly through the successive induction heating coils 250, the amountof heat generated therein is partly dependent upon the speed of travelof the metal straps 51 and the voltage fed to the induction heatingcoils 250. In the configuration as shown in FIG. 8, the control circuit275 is in its automatic mode, wherein the control circuit 275automatically adjusts for variations in speed and temperature of themetal straps 51 as they pass through the successive heating coils 250.The automatic mode of the control circuit 275 is shown herein, whereinthe function generator 280 is con nected to the DC amplifier 285, theswitch contacts 297 are in the closed position thereof, the switchcontacts 298 are in the open position thereof, and the switch 362 is inthe position illustrated. With the control circuit 275 in the automaticmode thereof, the tachometer 320 senses the speed of the the driedpainted metal straps 52 and sends the signal to the potentiometer 330which thereafter sends the output signal thereof via the conductor 335to the function generator 280. The function generator 280 automaticallygenerates a larger signal in response to increased speed of the metalstraps 52 through the induction heating coils 250, thereby to cause theoutput of the heating coils 250 to be greater and the heating of themetal straps 52 passing therethrough to be the same regardless of thespeed of the metal straps 52, the preferred speed of the metal straps 52being about 500 fL/min. and the induction heating coils being preferablyoperated at about 200 kilohertz. 1f the speed of the metal straps 52 istoo low, for instance below about 50 ft./min., the low speed limitcircuit 324, which also receives an input from the tachometer 320, sendsthe output signal therefrom via the conductor 303 to the functiongenerator 280, thereby to cease the heating, via the induction heatingcoils 250, of the metal straps 52. As is seen, the output signal fromthe function generator 280 is fed to the DC amplifier 285 which controlsthe SCR voltage controls 296 that in turn control the RF oscillators316, thereby directly to control the output of the induction heatingcoils 250 in response to the speed of the metal strap 52 therethrough.

lll

As a final control, the infrared sensing head 340 senses the temperatureof the metal straps 52 upon leaving the topmost induction heating coil250. The recorder 323 which receives inputs from both the tachometer 320and the infrared sensor 340 via the DC amplifier 344 provides a visualrecord of the temperature of the metal straps 52 as compared to thespeed of the metal straps 52 as the metal straps 52 leave the topmostinduction heating coil 250. In the comparator 347, the output from theDC amplifier 344, which reflects the temperature of the metal straps 52leaving the topmost induction heating coil 250, is compared with asignal from the temperature set potentiometer 350, which signal sets arange for the desired temperature of the metal straps 52 leaving thetopmost induction heating coil 250. When the temperature of the driedmetal straps 52 is greater or less than the predetermined temperaturerange set in the potentiometer 350, the comparator 347 produces a signalwhich after amplification by the DC amplifier 360 activates thereversible motor 365 which mechanically varies the position of thesliding contact on the potentiometer 330, thereby to vary the inputsignal to the function generator 280 in response to the temperature ofthe metal straps 52 leaving the topmost induction heating coil 250. Asis seen therefore, when the control circuit 275 is in the auto maticmode thereof, the output from the induction heating coils 250 iscontrolled both by the speed of the dried painted metal straps 52 asthey pass through the paint-drying station 110 and the temperature ofthe dried painted metal straps 52 as they exit from the topmostinduction heating coil 250.

When the control circuit 275 is in the manually controlled mode thereof,the DC amplifier 285 is connected to the manually controlledpotentiometer 286, whereby the signal from the DC amplifier 285 may bemanually controlled by adjustment of the sliding contact of thepotentiometer 286. Manual control of the control circuit 275 is alsoprovided by energizing the relay 305 to open the normally closed switchcontacts 297 and close the normally open switch contacts 298 to permitmanual control via manipulation of the sliding contacts on thepotentiometers 300 of the SCR voltage controls 296 and hence, the RFoscillators 316 and the output from the induction heating coils 250. Thecontrol circuit 275 is operable both manually to adjust the output ofthe induction heating coils 250 or automatically to adjust the output ofthe induction heating coils 250, the control circuit 275 in theautomatic mode thereof varying the output of the induction heating coils250 in response both to the speed of the metal straps 52 and thetemperature of the metal straps 52 leaving the topmost of the inductionheating coils 250.

It is seen therefore, that there has been provided a system forcontinuously drying a painted continuously moving metal strap 52. Thesystem comprises a drying station 110 including an induction heatingcoil 250 for heating the metal strap 52 to dry the paint thereon, drivemechanism 75 for continuously passing the metal strap 52 through theinduction heating coil 250 and a variable power supply in the form of afunction generator 280 for the induction heating coil 250 forcontrolling the output therefrom. The system further includes thetachometer 320 for sensing the speed of the movement of the metal strap52 with respect to the induction heating coil 250, the infrared sensor340 for sensing the temperature of the painted metal straps 52immediately after the passage thereof from the induction heating coil250, and a control circuit 275 responsive to the tachometer 320 and tothe infrared sensor 340 for controlling the function generator 280 andthus the heating produced by the induction heating coil 250 to heat the.painted metal strap 52 to a predetermined temperature at thetemperature sensing means. The control circuit 275 also includes limitmeans in the form of the low-speed limit circuit 324 responsive to thetachometer 320 for deenergizing the induction heating coil 250 when thespeed of the metal strap 52 with respect to the induction heating coil250 is below a predetermined value, to dry the paint on the metal strap52 throughout the length thereof passing through the induction heatingcoil 250 without burning the metal strap 52 or the paint thereon.

The term electrophoresis as used herein includes electrodepositionwherein the paint solids exist as discrete particles, as in an emulsion,and electrodeposition wherein the paint solids are in solution. The termstrap as used herein includes strips, wires and other forms ofcontinuous metal work pieces.

While there has been described what is at present considered to be thepreferred embodiment of the invention, it will be understood thatvarious modifications may be made therein, and it is intended to coverin the appended claims all such modifications as fall within the truespirit and scope of the invention.

What is claimed is:

l. A system for continuously applying paint to a continuously movingmetal strap and continuously drying the paint thereon, said systemcomprising, a paint-applying station including a paint pot and anelectrophoretic paintdistributing apparatus therein for applying auniform coating of paint to the metal strap, a paint-drying stationincluding an induction coil for heating the metal strap to dry the paintthereon, drive mechanism for continuously passing the metal strap from asource thereof through said paint pot and said electrophoreticpaint-distributing apparatus and then through said induction heatingcoil, a source of paint solids in communication with said paint pot,means for continually sensing the power consumed in said electrophoreticpaint-distributing apparatus, means for continually sensing theconcentration of paint solids in said paint pot, a first control circuitresponsive to said power consumption sensing means and said paint solidsconcentration sensing means for maintaining the concentration of paintsolids and the paint level in said paint pot within predeterminedvalues, a variable power supply for said induction heating coil forcontrolling the output therefrom, means for sensing the speed ofmovement of the metal strap with respect to said induction coil, meansfor sensing the temperature of the painted metal strap immediately afterpassage thereof from said induction heating coil, and a second controlcircuit responsive to said metal strap speed sensing means and to saidpainted strap temperature sensing means for controlling said variablepower supply and thus the heating produced by said induction heatingcoil to heat the painted metal strap to a predetermined temperature atsaid tempera ture-sensing means, whereby to apply to said metal strap auniform coating of paint uniformly dried thereon throughout the lengththereof.

2. The system set forth in claim 1, wherein said paint pot has disposedtherein a liner of a synthetic plastic resin.

3. The system set forth in claim 1, wherein said electrophoreticpaintdistributing apparatus includes means for providing the metal strapin said paint pot with a positive charge and for providing the paintsolids in said paint pot with a negative charge.

4. The system set forth in claim 1, wherein said power consumptionsensing means is adapted to produce a signal in response to theconsumption of a predetermined amount of power by said electrophoreticpaint-distributing means to control the transfer of a predeterminedamount of paint solids from said paint solids source to said paint pot.

5. The system set forth in claim 1, wherein said power consumptionsensing means is adapted to produce a first signal in response to theconsumption of a predetermined amount of power by said electrophoreticpaint-distributing means, and said paint solids concentration sensingmeans is adapted to produce a second signal in response to theconcentration of solids in said paint pot, with means to utilize saidfirst and second signals in said first control circuit jointly tocontrol the transfer of paint solids from the source thereof to saidpaint pot.

6. The system set forth in claim 1, and further comprising a variablepower supply for said electrophoretic paint-distributing means forcontrolling the charge imparted thereby, means for sensing the speed ofmovement of the metal strap with respect to said electrophoreticpaint-distributing means, and control mechanism responsive to saidspeed-sensing means for controlling said variable power source and thusthe charge produced by said electrophoretic paint-distributing means tomaintain the charge imparted to the metal strap within a predeterminedvalue.

7. The system set forth in claim 1, wherein said paint-drying stationincludes a plurality of induction coils for heating the metal strap.

8. The system set forth in claim 1, wherein said paint-drying stationincludes a plurality of induction coils for heating the metal strap, anda corresponding plurality of variable power supplies for said inductionheating coils, each of said variable power supplies controlling theoutput from a corresponding one of said induction heating coils.

9. The system set forth in claim 1, wherein said temperature-sensingmeans includes an infrared sensing device.

10. The system set forth in claim 1, and further comprising a paintsolids pump in communication with said paint solids source and saidpaint pot to pump paint solids from said paint solids source to saidpaint pot, said paint solids pump being controlled by said first controlcircuit to maintain the concentration of paint solids in said paint potwithin a predetermined value.

11. The system set forth in claim I, wherein said metal strap speedsensing means is adapted to produce a first signal responsive to thespeed of the metal strap, and said metal strap temperature sensing meansis adapted to produce a second signal responsive to the temperature ofthe metal strap immediately after the passage thereof from saidinduction heating coil, with means to utilize said first and secondsignals in said second control circuit jointly to control the powerproduced by said variable power supply and thus the heating produced bysaid induction heating coil in the metal strap passing therethrough.

12. The system set forth in claim 1, and further comprising means forcontinually sensing the temperature of the paint in said paint pot,means for cooling the paint, and control mechanism responsive to saidtemperature-sensing means for controlling said cooling means to maintainthe temperature of the paint within a predetermined value.

13. The system set forth in claim 1, and further comprising means fordisconnecting said second control circuit from said variable powersupply and placing said variable power supply under manual control.

14. A system for continuously applying paint to a continuously movingmetal strap and continuously drying the paint thereon, said systemcomprising a paint-applying station including a paint pot and anelectrophoretic paint distributing apparatus therein for applying auniform coating of paint to the metal strap, a paint-drying stationincluding an induction coil for heating the metal strap to dry the paintthereon, drive mechanism for continuously passing the metal strap from asource thereof through said paint pot and said electrophoreticpaint-distributing apparatus and then through said induction heatingcoil, a source of paint solids in communication with said paint pot anda source of paint diluent in communication with said paint pot, meansfor continually sensing the power consumed in said electrophoreticpaint-distributing apparatus, means for continually sensing theconcentration of paint solids in said paint pot, means for continuallysensing the level of paint in said paint pot, a first control circuitresponsive to said power consumption sensing means and said paint solidsconcentration sensing means and said paint level sensing means formaintaining the concentration of paint solids and the paint level insaid paint pot within predetermined values, a variable power supply forsaid induction heating coil for controlling the output therefrom, meansfor sensing the speed of movement of the metal strap with respect tosaid induction coil, means for sensing the temperature of the paintedmetal strap immediately after passage thereof from said inductionheating coil, and a second control circuit responsive to said metalstrap speed sensing means and to said painted strap temperature sensingmeans for controlling said variable power supply and thus the heatingproduced by said induction heating coil to heat the painted metal strapto a predetermined temperature of said temperature-sensing means,whereby to apply to said metal strap a uniform coating a paint uniformlydried thereon throughout the length thereof.

15. A system for continuously applying paint to a continuously movingmetal strap and continuously drying the paint thereon, said systemcomprising a paint-applying station including a paint pot and anelectrophoretic paint distributing apparatus therein for applying auniform coating of paint to the metal strap, a paint-drying stationincluding an induction coil for heating the metal strap to dry the paintthereon, drive mechanism for continuously passing the metal strap from asource thereof through said paint pot and said electrophoreticpaint-distributing apparatus and then through said induction heatingcoil, a source of paint solids in communication with said paint pot, apaint solids pump in communication with said paint solids source forwithdrawing a predetermined amount of paint solids from said paintsolids source, a blender in communication with said paint solids pumpfor mixing the paint solids withdrawn by said paint solids pump fromsaid paint solids source with the paint in said paint pot, means forcontinually sensing the power consumed in said electrophoreticpaint-distributing apparatus, means for continually sensingtheconcentration of paint solids in said paint pot, a first control circuitresponsive to said power consumption sensing means and to said paintsolids sensing means for activating said paint solids pump to withdraw apredetermined amount of paint solids from said paint solids source formaintaining the concentration of paint solids within a predeterminedvalue, a variable power supply for said induction heating coil forcontrolling the output therefrom, means for sensing the speed ofmovement of the metal strap with respect to said induction heating coil,means for sensing the temperature of the painted metal strap immediatelyafter passage thereof from said induction heating coil, and a secondcontrol circuit responsive to said metal strap speed sensing means andto said painted strap temperature sensing means for controlling saidvariable power supply and thus the heating produced by said inductionheating coil to heat the painted metal strap to a predeterminedtemperature at said temperature-sensing means, whereby to apply to saidmetal strap a uniform coating of paint uniformly dried thereonthroughout the length thereof.

16. A system for continuously applying paint to a continuously movingmetal strap and continuously drying the paint thereon, said systemcomprising a paint-applying station ineluding a paint pot and anelectrophoretic paint-distributing apparatus therein for applying auniform coating of paint to the metal strap, a paint-drying stationincluding an induction coil for heating the metal strap to dry the paintthereon, drive mechanism for continuously passing the metal strap from asource thereof through said paint pot and said electrophoreticpaint-distributing apparatus and then through said induction heatingcoil, a source of paint solids in communication with said paint pot anda source of paint diluent in communication with said paint pot, a paintsolids pump in communication with said paint solids source forwithdrawing a predetermined amount of paint solids from said paintsolids source, a blender in communication with said paint solids pumpfor mixing the paint solids withdrawn by said paint solids pump fromsaid paint solids source with the paint in said paint pot, means forcontinually sensing the power consumed in said electrophoreticpaint-distributing apparatus, means for continually sensing theconcentration of the paint solids in said paint pot, and a first controlcircuit responsive to said power consumption sensing means and to saidpaint solids sensing means for activating said paint solids pump towithdraw a predetermined amount of paint solids from said paint solidssource for maintaining the concentration of paint solids within apredetermined value, means for continually sensing the level of paint insaid paint pot, and a second control circuit responsive to said paintlevel sensing means for connecting said source of paint diluent to saidpaint pot for maintaining the level of paint within a predeterminedvalue, a variable power supply for said induction heating coil forcontrolling the output therefrom, means for sensing the speed ofmovement of the metal strap with respect to said induction heating coil,means for sensing the temperature of the painted metal strap immediatelyafter passage thereof from said induction heating coil, and a thirdcontrol circuit responsive to said metal strap speed sensing means andto said painted strap temperature sensing means for controlling saidvariable power supply and thus the heating produced by said inductionheating coil to heat the painted metal strap to a predeterminedtemperature at said temperature-sensing means, whereby to apply to saidmetal strap a uniform coating of paint uniformly dried thereonthroughout the length thereof.

17. A system for continuously applying paint to a continuously movingmetal strap, said system comprising a paint-applying station including apaint pot and an electrophoretic distributing apparatus therein forapplying a uniform coating of paint to the metal strap, drive mechanismfor continuously passing the metal strap from a source thereof throughsaid paint pot and said electrophoretic distributing apparatus, a sourceof paint solids in communication with said paint pot and a source ofpaint diluent in communication with said paint pot, means forcontinually sensing the power consumed in said electrophoreticpaint-distributing apparatus, means for continually sensing theconcentration of the paint solids in said paint pot, means forcontinually sensing the level of paint in said paint pot, and a controlcircuit responsive to said power consumption sensing means and saidpaint solids concentration sensing means and said paint level sensingmeans for maintaining the concentration of paint solids and the paintlevel in said paint pot within predetermined values, whereby to apply tothe metal strap throughout the length of the strap passing through saidpaint pot a uniform coating of paint containing the substantiallyuniform amount of paint solids therein.

18. The system set forth in claim 17, and further comprising means formaintaining the temperature of the paint in said paint pot within arange from about 75 to about 100 F.

19. The system set forth in claim 17, further comprising means formaintaining the voltage supplied to said electrophoretic distributingapparatus within a range from about 50 volts to about 250 volts.

20. The system set forth in claim 17, further comprising means formaintaining the current density produced by the electrophoreticdistributing apparatus in the metal strap passing therethrough within arange from about 0.1 to about a./ft.

21. The system set forth in claim 17, wherein said source of paintdiluent is a source of deionized water.

22. The system set forth in claim 17, wherein said source of paintsolids is a source of water-soluble paint solids.

23, The system set forth in claim 17, wherein said paint level sensingmeans includes a float switch disposed in said paint pot, said floatswitch being adapted to be activated when the level of the paint in saidpaint pot is outside the predetermined value, and a solenoid valveoperatively disposed between said paint diluent source and said paintpot and activated by said float switch to admit paint diluent from saidpaint diluent source to said paint pot when the level of the paint insaid paint pot is outside of the predetermined value.

24. The system set forth in claim 17, further comprising means formaintaining the concentration of paint solids in said paint pot within arange from about 5 to about 15 percent by weight of the paint in saidpaint pot.

25. A system for continuously applying paint to a continuously movingmetal strap, said system comprising a paint-applying station including apaint pot and an electrophoretic distributing apparatus therein forapplying a uniform coating of paint to the metal strap, drive mechanismfor continuously passing the metal strap from a source thereof throughsaid paint pot and said electrophoretic distributing apparatus, a sourceof paint solids in communication with said paint pot, a paint solids pumin communication with said paint solids source for with rawing apredetermined amount of paint solids from said solids source, a blenderin communication with said paint solids pump for mixing the paint solidswithdrawn by said paint solids pump from said paint solids source withthe paint in said paint pot, means for continually sensing the powerconsumed in said electrophoretic paint-distributing apparatus, means forcontinually sensing the concentration of the paint solids in said paintpot, and a control circuit responsive to said power consumption sensingmeans and to said paint solids sensing means for activating said paintsolids pump to withdraw a predetermined amount of paint solids from saidpaint solids source for maintaining the concentration of paint solidswithin a predetermined value, whereby to apply to the metal strapthroughout the length of the strap passing through said paint pot auniform coating of paint containing a substantially uniform amount ofpaint solids therein.

26. A system for continuously applying paint to a continuously movingmetal strap, said system comprising a paint applying station including apaint pot and an electrophoretic distributing apparatus therein forapplying a uniform coating of paint to the metal strap, drive mechanismfor continuously passing the metal strap from a source thereof throughsaid paint pot and said electrophoretic distributing apparatus, a sourceof paint solids in communication with said paint pot, and a source ofpaint diluent in connection with said paint pot, a paint solids pump incommunication with said paint solids source for withdrawing apredetermined amount of paint solids from said solids source, a blenderin communication with said paint solids pump for mixing the paint solidswithdrawn by said paint solids pump from said paint solids source withthe paint in said paint pot, means for continually sensing the powerconsumed in said electrophoretic paint-distributing apparatus, means forcontinually sensing the concentration of the paint solids in said paintpot, and a first control circuit responsive to said power consumptionsensing means and to said paint solids sensing means for activating saidpaint solids pump to withdraw a predetermined amount of paint solidsfrom said paint solids source for maintaining the concentration of paintsolids within a predetermined value, means for continually sensing thelevel of paint in said paint pot, and a second control circuitresponsive to said paint level sensing means for connecting said sourceof paint diluent to said paint pot for maintaining the level of paintwithin a predetennincd value, whereby to apply to the metal strapthroughout the length of the strap passing through said paint pot auniform coating of paint containing a substantially uniform amount ofpaint solids therein.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,616,459 Dated October ze 1971 I t Richard S. Patton, Naaman H. Keyser,Vernon L.

Tangdon, V1ctor D. Beauoaire, Louis A. Marlin It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

In the references:

"Plenser" should be Plensler Signe d and sealed tn 9th day of 31.17;1972.

(SEAL) Latest:

A lite s Ling Officer C ormfnissione 1" of Pa be nts )RM Po-IOSO (10-69)USCOMM-DC suave-ps9 9 U S GOVERNMENF PRINTFNG OFFKCE I959 O3563J4

2. The system set forth in claim 1, wherein said paint pot has disposedtherein a liner of a synthetic plastic resin.
 3. The system set forth inclaim 1, wherein said electrophoretic paint-distributing apparatusincludes means for providing the metal strap in said paint pot with apositive charge and for providing the paint solids in said paint potwith a negative charge.
 4. The system set forth in claim 1, wherein saidpower consumption sensing means is adapted to produce a signal inresponse to the consumption of a predetermined amount of power by saidelectrophoretic paint-distributing means to control the transfer of apredetermined amount of paint solids from said paint solids source tosaid paint pot.
 5. The system set forth in claim 1, wherein said powerconsumption sensing means is adapted to produce a first signal inresponse to the consumption of a predetermined amount of power by saidelectrophoretic paint-distributing means, and said paint solidsconcentration sensing means is adapted to produce a second signal inresponse to the concentration of solids in said paint pot, with means toutilize said first and second signals in said first control circuitjointly to control the transfer of paint solids from the source thereofto said paint pot.
 6. The system set forth in claim 1, and furthercomprising a variable power supply for said electrophoreticpaint-distributing means for controlling the charge imparted thereby,means for sensing the speed of movement of the metal strap with respectto said electrophoretic paint-distributing means, and control mechanismresponsive to said speed-sensing means for controlling said variablepower source and thus the charge produced by said electrophoreticpaint-distributing means to maintain the charge imparted to the metalstrap within a predetermined value.
 7. The system set forth in claim 1,wherein said paint-drying station includes a plurality of inductioncoils for heating the metal strap.
 8. The system set forth in claim 1,wherein said paint-drying station includes a plurality of inductioncoils for heating the metal strap, and a corresponding plurality ofvariable power supplies for said induction heating coils, each of saidvariable power supplies controlling the output from a corresponding oneof said induction heating coils.
 9. The system set forth in claim 1,wherein said temperature-sensing means includes an infrared sensingdevice.
 10. The system set forth in claim 1, and further comprising apaint solids pump in communication with said paint solids source andsaid paint pot to pump paint solids from said paint solids source tosaid paint pot, said paint solids pump being controlled by said firstcontrol circuit to maintain the concentration of paint solids in saidpaint pot within a predetermined value.
 11. The system set forth inclaim 1, wherein said metal strap speed sensing means is adapted toproduce a first signal responsive to the speed of the metal strap, andsaid metal strap temperature sensing means is adapted to produce asecond signal responsive to the temperature of the metal strapimmediately after the passage thereof from said induction heating coil,with means to utilize said first and second signals in said secondcontrol circuit jointly to control the power produced by said variablepower supply and thus the heating produced by said induction heatingcoil in the metal strap passing therethrough.
 12. The system set forthin claim 1, and further comprising means for continually sensing thetemperature of the paint in said paint pot, means for cooling the paint,and control mechanism responsive to said temperature-sensing means forcontrolling said cooling means to maintain the temperature of the paintwithin a predetermined value.
 13. The system set forth in claim 1, andfurther comprising means for disconnecting said second control circuitfrom said variable power supply and placing said variable power supplyunder manual control.
 14. A system for continuously applying paint to acontinuously moving metal strap and continuously drying the paintthereon, said system comprising a paint-applying station including apaint pot and an electrophoretic paint distributing apparatus thereinfor applying a uniform coating of paint to the metal strap, apaint-drying station including an induction coil for heating the metalstrap to Dry the paint thereon, drive mechanism for continuously passingthe metal strap from a source thereof through said paint pot and saidelectrophoretic paint-distributing apparatus and then through saidinduction heating coil, a source of paint solids in communication withsaid paint pot and a source of paint diluent in communication with saidpaint pot, means for continually sensing the power consumed in saidelectrophoretic paint-distributing apparatus, means for continuallysensing the concentration of paint solids in said paint pot, means forcontinually sensing the level of paint in said paint pot, a firstcontrol circuit responsive to said power consumption sensing means andsaid paint solids concentration sensing means and said paint levelsensing means for maintaining the concentration of paint solids and thepaint level in said paint pot within predetermined values, a variablepower supply for said induction heating coil for controlling the outputtherefrom, means for sensing the speed of movement of the metal strapwith respect to said induction coil, means for sensing the temperatureof the painted metal strap immediately after passage thereof from saidinduction heating coil, and a second control circuit responsive to saidmetal strap speed sensing means and to said painted strap temperaturesensing means for controlling said variable power supply and thus theheating produced by said induction heating coil to heat the paintedmetal strap to a predetermined temperature of said temperature-sensingmeans, whereby to apply to said metal strap a uniform coating a paintuniformly dried thereon throughout the length thereof.
 15. A system forcontinuously applying paint to a continuously moving metal strap andcontinuously drying the paint thereon, said system comprising apaint-applying station including a paint pot and an electrophoreticpaint distributing apparatus therein for applying a uniform coating ofpaint to the metal strap, a paint-drying station including an inductioncoil for heating the metal strap to dry the paint thereon, drivemechanism for continuously passing the metal strap from a source thereofthrough said paint pot and said electrophoretic paint-distributingapparatus and then through said induction heating coil, a source ofpaint solids in communication with said paint pot, a paint solids pumpin communication with said paint solids source for withdrawing apredetermined amount of paint solids from said paint solids source, ablender in communication with said paint solids pump for mixing thepaint solids withdrawn by said paint solids pump from said paint solidssource with the paint in said paint pot, means for continually sensingthe power consumed in said electrophoretic paint-distributing apparatus,means for continually sensing the concentration of paint solids in saidpaint pot, a first control circuit responsive to said power consumptionsensing means and to said paint solids sensing means for activating saidpaint solids pump to withdraw a predetermined amount of paint solidsfrom said paint solids source for maintaining the concentration of paintsolids within a predetermined value, a variable power supply for saidinduction heating coil for controlling the output therefrom, means forsensing the speed of movement of the metal strap with respect to saidinduction heating coil, means for sensing the temperature of the paintedmetal strap immediately after passage thereof from said inductionheating coil, and a second control circuit responsive to said metalstrap speed sensing means and to said painted strap temperature sensingmeans for controlling said variable power supply and thus the heatingproduced by said induction heating coil to heat the painted metal strapto a predetermined temperature at said temperature-sensing means,whereby to apply to said metal strap a uniform coating of paintuniformly dried thereon throughout the length thereof.
 16. A system forcontinuously applying paint to a continuously moving metal strap andContinuously drying the paint thereon, said system comprising apaint-applying station including a paint pot and an electrophoreticpaint-distributing apparatus therein for applying a uniform coating ofpaint to the metal strap, a paint-drying station including an inductioncoil for heating the metal strap to dry the paint thereon, drivemechanism for continuously passing the metal strap from a source thereofthrough said paint pot and said electrophoretic paint-distributingapparatus and then through said induction heating coil, a source ofpaint solids in communication with said paint pot and a source of paintdiluent in communication with said paint pot, a paint solids pump incommunication with said paint solids source for withdrawing apredetermined amount of paint solids from said paint solids source, ablender in communication with said paint solids pump for mixing thepaint solids withdrawn by said paint solids pump from said paint solidssource with the paint in said paint pot, means for continually sensingthe power consumed in said electrophoretic paint-distributing apparatus,means for continually sensing the concentration of the paint solids insaid paint pot, and a first control circuit responsive to said powerconsumption sensing means and to said paint solids sensing means foractivating said paint solids pump to withdraw a predetermined amount ofpaint solids from said paint solids source for maintaining theconcentration of paint solids within a predetermined value, means forcontinually sensing the level of paint in said paint pot, and a secondcontrol circuit responsive to said paint level sensing means forconnecting said source of paint diluent to said paint pot formaintaining the level of paint within a predetermined value, a variablepower supply for said induction heating coil for controlling the outputtherefrom, means for sensing the speed of movement of the metal strapwith respect to said induction heating coil, means for sensing thetemperature of the painted metal strap immediately after passage thereoffrom said induction heating coil, and a third control circuit responsiveto said metal strap speed sensing means and to said painted straptemperature sensing means for controlling said variable power supply andthus the heating produced by said induction heating coil to heat thepainted metal strap to a predetermined temperature at saidtemperature-sensing means, whereby to apply to said metal strap auniform coating of paint uniformly dried thereon throughout the lengththereof.
 17. A system for continuously applying paint to a continuouslymoving metal strap, said system comprising a paint-applying stationincluding a paint pot and an electrophoretic distributing apparatustherein for applying a uniform coating of paint to the metal strap,drive mechanism for continuously passing the metal strap from a sourcethereof through said paint pot and said electrophoretic distributingapparatus, a source of paint solids in communication with said paint potand a source of paint diluent in communication with said paint pot,means for continually sensing the power consumed in said electrophoreticpaint-distributing apparatus, means for continually sensing theconcentration of the paint solids in said paint pot, means forcontinually sensing the level of paint in said paint pot, and a controlcircuit responsive to said power consumption sensing means and saidpaint solids concentration sensing means and said paint level sensingmeans for maintaining the concentration of paint solids and the paintlevel in said paint pot within predetermined values, whereby to apply tothe metal strap throughout the length of the strap passing through saidpaint pot a uniform coating of paint containing the substantiallyuniform amount of paint solids therein.
 18. The system set forth inclaim 17, and further comprising means for maintaining the temperatureof the paint in said paint pot within a range from about 75* to about100* F.
 19. THe system set forth in claim 17, further comprising meansfor maintaining the voltage supplied to said electrophoreticdistributing apparatus within a range from about 50 volts to about 250volts.
 20. The system set forth in claim 17, further comprising meansfor maintaining the current density produced by the electrophoreticdistributing apparatus in the metal strap passing therethrough within arange from about 0.1 to about 5 a./ft.2.
 21. The system set forth inclaim 17, wherein said source of paint diluent is a source of deionizedwater.
 22. The system set forth in claim 17, wherein said source ofpaint solids is a source of water-soluble paint solids.
 23. The systemset forth in claim 17, wherein said paint level sensing means includes afloat switch disposed in said paint pot, said float switch being adaptedto be activated when the level of the paint in said paint pot is outsidethe predetermined value, and a solenoid valve operatively disposedbetween said paint diluent source and said paint pot and activated bysaid float switch to admit paint diluent from said paint diluent sourceto said paint pot when the level of the paint in said paint pot isoutside of the predetermined value.
 24. The system set forth in claim17, further comprising means for maintaining the concentration of paintsolids in said paint pot within a range from about 5 to about 15 percentby weight of the paint in said paint pot.
 25. A system for continuouslyapplying paint to a continuously moving metal strap, said systemcomprising a paint-applying station including a paint pot and anelectrophoretic distributing apparatus therein for applying a uniformcoating of paint to the metal strap, drive mechanism for continuouslypassing the metal strap from a source thereof through said paint pot andsaid electrophoretic distributing apparatus, a source of paint solids incommunication with said paint pot, a paint solids pump in communicationwith said paint solids source for withdrawing a predetermined amount ofpaint solids from said solids source, a blender in communication withsaid paint solids pump for mixing the paint solids withdrawn by saidpaint solids pump from said paint solids source with the paint in saidpaint pot, means for continually sensing the power consumed in saidelectrophoretic paint-distributing apparatus, means for continuallysensing the concentration of the paint solids in said paint pot, and acontrol circuit responsive to said power consumption sensing means andto said paint solids sensing means for activating said paint solids pumpto withdraw a predetermined amount of paint solids from said paintsolids source for maintaining the concentration of paint solids within apredetermined value, whereby to apply to the metal strap throughout thelength of the strap passing through said paint pot a uniform coating ofpaint containing a substantially uniform amount of paint solids therein.26. A system for continuously applying paint to a continuously movingmetal strap, said system comprising a paint applying station including apaint pot and an electrophoretic distributing apparatus therein forapplying a uniform coating of paint to the metal strap, drive mechanismfor continuously passing the metal strap from a source thereof throughsaid paint pot and said electrophoretic distributing apparatus, a sourceof paint solids in communication with said paint pot, and a source ofpaint diluent in connection with said paint pot, a paint solids pump incommunication with said paint solids source for withdrawing apredetermined amount of paint solids from said solids source, a blenderin communication with said paint solids pump for mixing the paint solidswithdrawn by said paint solids pump from said paint solids source withthe paint in said paint pot, means for continually sensing the powerconsumed in said electrophoretic paint-distributing apparatus, means forcontinually sensing the concentration of the paint solids in saId paintpot, and a first control circuit responsive to said power consumptionsensing means and to said paint solids sensing means for activating saidpaint solids pump to withdraw a predetermined amount of paint solidsfrom said paint solids source for maintaining the concentration of paintsolids within a predetermined value, means for continually sensing thelevel of paint in said paint pot, and a second control circuitresponsive to said paint level sensing means for connecting said sourceof paint diluent to said paint pot for maintaining the level of paintwithin a predetermined value, whereby to apply to the metal strapthroughout the length of the strap passing through said paint pot auniform coating of paint containing a substantially uniform amount ofpaint solids therein.